Gas turbines are widely used in commercial operations for power generation. Operating that gas turbine at higher temperatures generally increases the thermodynamic efficiency of the gas turbine. However, higher operating temperatures often produce localized hot spots in the combustors near the nozzle exits if fuel and air are not well mixed prior to combustion. Localized hot spots may increase the chance for flame flash back and flame holding. Flame flash back and flame holding may occur with any fuel and are especially associated with high reactive fuels, such as hydrogen fuel, which has a much higher burning rate and much wider flammability range than fuels having a lower reactivity. Flame flash back and flame holding should be avoided during operations as the nozzles may be burnt at such events. In addition, uneven fuel/air mixing with the localized hot spot increases the generation of NOx, and uneven fuel/air mixing with the localized cold spots increases the emission of carbon monoxide and unburned hydrocarbons, all of which are undesirable exhaust emissions.
A variety of techniques exist to allow higher operating temperatures while minimizing localized hot spots and undesirable emissions. For example, various nozzles have been developed to more uniformly mix the fuel with the working fluid prior to combustion. A more uniform fuel mixture allows the gas turbine to operate on a near fully premixed combustion that produces fewer hot spots and generates lower emissions. Flame holding and flame flash back happen when the flame burning velocity is higher than the local flow velocity. To prevent flame holding or flash back, flow velocity needs to be increased which often requires an additional pressure drop across the nozzles, and the pressure drop across the nozzles detracts from the overall thermodynamic efficiency of the gas turbine.
Therefore, the continued need exists for an improved nozzle that can support increasingly higher combustion temperatures and high reactive fuels while minimizing localized hot spots, flame holding, and the pressure drop across the nozzle.